An electric power cable comprises at least one electrical conductor which is surrounded by an insulating material. An outer jacket portion surrounds the electrical conductor. Further members may be arranged underneath the outer jacket portion, such as an electrical shielding, enforcing wires, etc. Electric power cables are advantageously bendable to a certain extent in order to be handled prior, during, and after installation.
Some electric power cables are suspended between suspension points. Such an electric power cable may be self-supporting, i.e. designed to support forces related to its own weight and also to external forces affecting the self-supporting electric power cable. At least one conductor in an inner portion of the self-supporting electric power cable or at least one messenger wire in the inner portion of the self-supporting electric power cable is designed to bear these forces. A conductor may comprise several wires that are made out of aluminium and/or copper. One solution is therefore to let the conductor itself act as the supporting element. At a suspension point of a self-supporting electric power cable, forces acting on the self-supporting electric power cable are transferred via a suspension arrangement to a carrying structure for the self-supporting electric power cable. Various kinds of suspension arrangements for over-head electric power cables are known. Some kinds of suspension arrangements engage with an exterior surface of the self-supporting electric power cable and thus, the forces have to be transferred between an outer portion comprising the exterior surface and the inner portion of the self-supporting electric power cable. WO 2012/005638 discloses a self-supporting electric power cable comprising an intermediate layer arranged between an outer portion and an inner portion of the self-supporting electric power cable. Relative movement between the inner and outer portions is permitted. At a suspension point, where the self-supporting electric power cable is subjected to radial forces from a suspension arrangement, the intermediate layer provides a frictional engagement between the inner and outer portions, by means of which forces acting along the self-supporting electric power cable may be transferred between the inner and outer portions.
U.S. Pat. No. 4,956,523 discloses an armoured electric cable having integral tensile members made e.g. from steel or aramid fibres to provide additional tensile strength. The tensile members are embedded in an inner PVC jacket which securely grips the central insulated conductors over which it is extruded. The jacket is, in turn, securely gripped by an armour cover formed of a steel strip which is wound helically around the jacket and bites into longitudinal ridges on the jacket. The armour coating has an undulating shape and is covered by an outer PVC jacket which is extruded over it. Thus, in the vertical position much of the weight of the insulated conductors, inner and outer PVC jackets and armour coating can be supported by the tensile members without producing dangerous longitudinal slippage or creepage between them.
US 2007/0044992 discloses a subsea power cable including a conductor encompassed by a layer of high voltage insulation material including inner and outer semiconducting layers. The insulated conductor is encompassed by a number of armouring elements each consisting of polyaramid fibres enclosed within a semi-conductive layer. US 2007/0044992 attempts to solve the problem with squeezing between a pipeline and hard objects during installation of the subsea power cable. Moreover, as the pipeline expands and contracts during operation, the cable is generally subject to stretching and sliding forces against the seabed. These problems are aggravated, if the pipeline spans valleys between reefs or boulders on the seabed. The subsea cable proposed in US 2007/0044992 attempts at least to alleviate these problems.